In recent years, from a perspective of preserving the environment, it is becoming popular to use a power generating apparatus of renewable energy type such as a wind turbine generator utilizing wind power and a power generating apparatus utilizing tidal current, ocean current or river current. In the power generating apparatus of renewable energy type, the kinetic energy of the wind, tidal current, river current or the like is converted to the rotation energy of the rotor and the rotation energy of the rotor is then converted into electric power by the generator.
In a general power generating apparatus of renewable energy type, the rotation of the rotor is small compared to the rated rotation speed of the generator and thus, it is common to provide a mechanical step-up gear between the rotor and the generator. By this, the rotation of the rotor is increased to the rated rotation speed of the generator and then the increased rotation is inputted to the generator.
When performing maintenance or fixing the power generating apparatus of renewable energy type, the rotor is fixed (locked) sometimes.
For instance, Patent Literature 1 proposes to stop the rotor in a desired rotational position by applying a braking force to the rotor by a brake mechanism and then to lock the rotor with a locking pin in the desired rotational position. Specifically, the rotor is decelerated by the brake mechanism constituted of a brake disk and a brake shoe and the rotational position of the rotor is detected by a position sensor, and once the rotor comes to a standstill at the desired rotational position, the locking pin is automatically inserted into a locking disk.
In recent years, a development of a power generating apparatus of renewable energy type equipped with a hydraulic transmission formed by a hydraulic pump and a hydraulic motor is promoted, instead of a conventional apparatus equipped with the step-up gear, which makes it difficult to reduce the weight and the cost of the apparatus. Such power generating apparatus of renewable energy type is also disclosed in Patent Literatures 2 and 3.